Extendible Stent Apparatus

ABSTRACT

The present invention concerns novel stent apparatuses for use in treating lesions at or near the bifurcation point in bifurcated cardiac, coronary, renal, peripheral vascular, gastrointestinal, pulmonary, urinary and neurovascular vessels and brain vessels. More particularly, the invention concerns a stent apparatus with at least one side opening which may further comprise an extendable stent portion laterally extending from the side opening and at least partly in registry with the wall of the side opening. Devices constructed in accordance with the invention include, singularly or in combination, a main expandable stent comprising at least one substantially circular side opening located between its proximal and distal end openings, which side opening may further comprise an expandable portion extending radially outward from the edges of the side opening; and a branch stent comprising proximal and distal end openings and which may further comprise a contacting portion at its proximal end, and which may optionally be constructed to form either a perpendicular branch or a non-perpendicular branch when inserted through a side opening of the main stent. The stents of the invention are marked with, or at least partially constructed of, a material which is imageable during intraluminal catheterization techniques, most preferably but not limited to ultrasound and x-ray.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 12/472189,filed May 26, 2009, which is a Continuation of application Ser. No.11/545254, filed Oct. 10, 2006, now U.S. Pat. No. 7,537,609, which is aContinuation of application Ser. No. 10/683,165, filed Oct. 14, 2003,now U.S. Pat. No. 7,118,593, which is a Continuation of application Ser.No. 09/963,114, filed on Sep. 24, 2001, now U.S. Pat. No. 6,706,062,which is a Continuation of application Ser. No. 09/326,445, filed onJun. 4, 1999, now U.S. Pat. No. 6,325,826, which claims priority toProvisional Application No. 60/088301, filed Jun. 5, 1998 and is acontinuation-in-part of PCT application No. PCT/US99/00835, filed onJan. 13, 1999, the contents of each of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

A type of endoprosthesis device, commonly referred to as a stent, may beplaced or implanted within a vein, artery or other tubular body organfor treating occlusions, stenoses, or aneurysms of a vessel byreinforcing the wall of the vessel or by expanding the vessel. Stentshave been used to treat dissections in blood vessel walls caused byballoon angioplasty of the coronary arteries as well as peripheralarteries and to improve angioplasty results by preventing elastic recoiland remodeling of the vessel wall. Two randomized multicenter trialshave recently shown a lower restenosis rate in stent treated coronaryarteries compared with balloon angioplasty alone (Serruys, P W et al.New England Journal of Medicine 331: 489-495, 1994, Fischman, D L et al.New England Journal of Medicine 331: 496-501, 1994). Stents have beensuccessfully implanted in the urinary tract, the bile duct, theesophagus and the tracheo-bronchial tree to reinforce those body organs,as well as implanted into the neurovascular, peripheral vascular,coronary, cardiac, and renal systems, among others. The term “stent” asused in this Application is a device which is intraluminally implantedwithin bodily vessels to reinforce collapsing, dissected, partiallyoccluded, weakened, diseased or abnormally dilated or small segments ofa vessel wall.

One of the drawbacks of conventional stents is that they are generallyproduced in a straight tubular configuration. The use of such stents totreat diseased vessels at or near a bifurcation (branch point) of avessel may create a risk of compromising the degree of patency of theprimary vessel and/or its branches, or the bifurcation point and alsolimits the ability to insert a second stent into the side branch if theresult of treatment of the primary, or main, vessel is suboptimal.Suboptimal results may occur as a result of several mechanisms, such asdisplacing diseased tissue, plaque shifting, vessel spasm, dissectionwith or without intimal flaps, thrombosis, and embolism.

The risk of branch compromise is increased generally in two anatomicalsituations. First, a side branch may be compromised when there is astenosis in the origin of the side branch. Second, when there is aneccentric lesion at the bifurcation site, asymmetric expansion can causeeither plaque shifting or dissection at the side branch origin. Thereare reports of attempts to solve this problem by inserting a ballooninto the side branch through the struts of a stent deployed in the mainbranch spanning the bifurcation point; however, this technique carriesthe risk of balloon entrapment and other major complications (Nakamura,S. et al., Catheterization and Cardiovascular Diagnosis 34: 353-361(1995)). Moreover, adequate dilation of the side branch is limited byelastic recoil of the origin of the side branch. In addition, insertionof a traditional stent into a main vessel spanning the bifurcation pointmay pose a limitation to blood flow and access to the side branchvessel. The term “stent jail” is often used to describe this concept. Inthis regard, the tubular slotted hinged design of the Palmaz-Schatzintracoronary stent, in particular, is felt to be unfavorable forlesions with a large side branch and is generally believed to pose ahigher risk of side branch vessel entrapment where the stent prevents orlimits access to the side branch. Id.

One common procedure for intraluminally implanting a stent is to firstopen the relevant region of the vessel with a balloon catheter and thenplace the stent in a position that bridges the treated portion of thevessel in order to prevent elastic recoil and restenosis of thatsegment. The angioplasty of the bifurcation lesion has traditionallybeen performed using the “kissing” balloon technique where twoguidewires and two balloons are inserted, one into the main branch andthe other into the side branch. Stent placement in this situationrequires the removal of the guidewire from the side branch andreinsertion through the stent struts, followed by the insertion of aballoon through the struts of the stent along the guidewire. The firstremoval of the guidewire poses the risk of occlusion of the side branchduring the deployment of the stent in the main branch.

In general, when treating a bifurcation lesion using commerciallyavailable stents, it is important to cover the origin of the branchbecause if left uncovered, this area is prone to restenosis. In order tocover the branch origin, conventional stents inserted into the branchmust protrude into the lumen of the main artery or vessel from thebranch (which may cause thrombosis, again compromising blood flow).Another frequent complication experienced when stenting bifurcatedvessels is the narrowing or occlusion of the origin of a side branchspanned by a stent placed in the main branch. Additionally, placement ofa stent into a main vessel where the stent partially or completelyextends across the opening of a branch makes future access into suchbranch vessels difficult if not impossible. As a result, conventionalstents are often placed into the branch close to the origin, butgenerally not covering the origin of the bifurcation.

Lastly, conventional stents are difficult to visualize during and afterdeployment, and in general are not readily imaged by using low-cost andeasy methods such as x-ray or ultrasound imaging. While some prior artballoon catheters (and not stents) are “marked” at the proximal anddistal ends of the balloon with imageable patches, few stents arecurrently available which are marked with or which are at least partlyconstructed of, a material which is imageable by currently known imagingprocedures commonly used when inserting the stents into a vessel, suchas ultrasound or x-ray imaging. The invention described in thisApplication would not work with endoscopy as currently used as animaging method due to size limitations, but future advances in limitingthe size of endoscopic imaging devices may in the future make endoscopicimaging compatible with the stents of the invention.

Accordingly, there is a need for improved stent apparatuses, mostparticularly for applications within the cardiac, coronary, renal,peripheral vascular, gastrointestinal, pulmonary, urinary andneurovascular systems and the brain which 1) completely covers thebifurcation point of bifurcation vessels; 2) may be used to treatlesions in one branch of a bifurcation while preserving access to theother branch for future treatment; 3) allows for differential sizing ofthe stents in a bifurcated stent apparatus even after the main stent isimplanted; 4) may be delivered intraluminally by catheter; 5) may beused to treat bifurcation lesions in a bifurcated vessel where thebranch vessel extends from the side of the main vessel; and 6) is markedwith, or at least partly constructed of, material which is imageable bycommonly used intraluminal catheterization visualization techniquesincluding but not limited to ultrasound or x-ray.

SUMMARY OF THE INVENTION

The present invention concerns novel stent apparatuses for methods, andkits use in treating lesions at or near the bifurcation point inbifurcated vessels. More particularly, the invention concerns a stentapparatus with a main tubular stent body having at least one sideopening which may further comprise an extendable or second stentinserted through the side opening and at least partly in registry withthe wall of the side opening.

As used herein, the term “vessel” means any body lumen or tubular tissuewithin the cardiac, coronary, renal, peripheral vascular,gastrointestinal, pulmonary, urinary and neurovascular systems and thebrain. Devices constructed in accordance with the invention include,singularly or in combination, a main expandable tubular stent bodyhaving at least one side opening (usually substantially circular)located between its proximal and distal end openings, which side openingmay further comprise a radially expandable portion extending laterallyoutward from the edges of the side opening; and an expandable branchsecond stent comprising proximal and distal end openings and which mayfurther comprise a contacting portion at its proximal end, and which maybe constructed to form an angularly variable branched stent apparatuswhen inserted through a side opening of the main stent. The radiallyexpandable portion preferably comprises a plurality of laterallydeployable elements, such as loops, tabs, beams, or the like, attachedor coupled to a peripheral edge of the side opening. Usually, theelements will project inwardly from the periphery into the side hole sothat they may be deployed radially outwardly from the periphery to openin a petal-like fashion. The elements may be formed integrally as partof the tubular body structure, e.g., being formed from the bent wire orband or from the cut tubular structure which defines the stentstructure. Alternatively, they could be formed separately andsubsequently attached by crimping, welding, folding, interferencefitting, etc. Optionally, the expandable portion may be covered with afabric or the entire stent structure membrane to help form thetransition between the main body lumen and the lumen of the secondstent. The stents of the invention are marked with, or at leastpartially constructed of, a material which is imageable duringintraluminal catheterization techniques, most preferably but not limitedto ultrasound and x-ray, preferably being radiopaque.

In a preferred aspect of the stent design, the side hole will be definedby a continuous band or pattern of material which defines the peripheryof the side hole. The band may have a circular, oval, or other regulargeometry in which case the width and area of the side hole will remaingenerally constant as the stent is expanded. Alternatively, thecontinuous band may comprise discontinuities over its length so that thearea and/or width of the side hole may expand together with the stentstructure. Preferably, the continuous band will include inwardlyprojecting loops, fingers, or other protrusions which will define thelaterally deployable elements which project inwardly from the peripheraledge of the side opening. The inwardly projecting loops or otherelements may be overlapping or non-overlapping. The use of overlappinglooped structures maximizes the length of the inwardly projectingelements after they are unfolded and opened inwardly into the sidebranch, as described in more detail below.

In another aspect of the present invention, a stent for placement in abifurcated body lumen comprises a main tubular body having a first end,a second end, and a side opening therebetween. A first portion of themain tubular body between the first end and the side hole opens inresponse to a first radially outward pressure, typically provided by anexpansion balloon. A second portion of the main tubular body between theside hole and the second end opens in response to a second pressure,again typically applied by an expansion balloon. By constructing themain tubular body so that the first opening pressure is less than thesecond opening pressure, the stent can have differential openingcharacteristics. That is, by introducing a balloon expansion catheterinto the stent and applying a constant pressure over the entire lengthof the balloon, the first portion of the stent will yield and openbefore the second portion of the stent. The particular embodimentsdescribed below, the first yield pressure will typically be in the rangefrom 1 atmospheres to 10 atmospheres while the second yield pressurewill typically be in the range from 2 atmospheres to 18 atmospheres.Such stent structures may be placed by initially opening and deployingthe first portion, typically the proximal portion on the same side ofthe bifurcation as the deployment catheter, and thereafter positioningthe side hole to align more precisely with the bifurcated secondaryblood vessel. After the proper positioning has been achieved, the secondstent portion can then be opened, conveniently using the same expansionballoon which has been inflated to a higher inflation pressure. Suchstents will typically include the laterally deployable elements disposedaround the side opening, as described above, and will optionally be usedin combination with secondary stents, as described above.

The stent structures as described previously may combine conventionalstent elements, such as serpentine rings, diamond or box structures,axial expansion members, and the like. In addition, in order to providethe differential expansion characteristics, the main tubular bodies ofthe stents may include axial spine structures which differ from theremaining portions of the tubular body of the stent. For example, thefirst portion of the stent may have an axial spine which readily expandscircumferentially. By then providing a spine section on the secondportion of the stent which is more resistant to circumferentialexpansion, the desired differential expansion will be achieved.Alternatively, the differential expansion can be achieved by employingstent patterns which are uniformly easier or more difficult to radiallyexpand over their entire peripheral length. Specific examples of bothstructures will be described below.

The stent apparatuses of the invention offers significant and noveladvantages over prior art stents in that the stents of the invention 1)can completely cover the bifurcation point of a branched vessel; 2) canaccommodate main and branch stents of differing sizes, thus providing abetter fit where the main and branch vessels are of different sizes orwhere the main and branch vessels are occluded to different degrees; 3)can fit branched vessels where the branch extends laterally from theside of the main vessel; 4) may be used to treat lesions in one branchof a bifurcation while preserving complete access to the other branchfor future treatment; 5) may be delivered intraluminally by catheter;and 6) are marked with, or at least partly constructed of, materialwhich is imageable by commonly used intraluminal catheterizationvisualization techniques including but not limited to ultrasound orx-ray, but not endoscopy.

Thus, it is an object of the present invention to provide both adouble-stent apparatus and a single-stent apparatus, each of which maybe used to cover the origin of a bifurcation in a branched vessel.

Another object of the invention is to provide a single-stent apparatuswhich may be used to treat only one branch of a bifurcation lesion whileleaving access to the second branch unobstructed.

Additionally, it is an object of the invention to provide a stentapparatus which is itself imageable by methods commonly used duringcatheterization such as x-ray or ultrasound.

Yet another object of the invention is to provide a bifurcatingdouble-stent device wherein the main stent and the branch stent orstents may be of different sizes.

Lastly, it is an important object of the invention to provide a stentapparatus which may be used to treat bifurcated vessels where the vesselbifurcation extends laterally from the side of the main vessel.

These objects and other object advantages and features of the inventionwill become better understood from the detailed description of theinvention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of the double-stent apparatus of thepresent invention in which both the main stent and the branch stent arefully dilated.

FIG. 2 is a schematic depiction of the main stent of the apparatus ofthe invention as deployed, with the side opening in registry with avessel bifurcation point.

FIG. 3 is a schematic depiction of the branch stent of the apparatus asdeployed, with the contacting portion fully expanded to contact theorigin of the bifurcated vessel.

FIG. 4 is a schematic depiction of the main stent of the apparatusdeployed within a subject vessel, after inflation of a balloon to expandthe main stent to fit the walls of the subject vessel.

FIG. 5 is a schematic depiction of the double-stent bifurcating stentapparatus, where the main stent is deployed and showing the placement ofthe branch stent apparatus prior to full deployment of the branch stent.

FIG. 6 a depicts initial placement of the main stent of the bifurcatingstent apparatus into the vessel, along with the insertion of a guidewireand stabilizing catheter for placement of the branch stent into thebranch vessel of the subject.

FIG. 6 b is a schematic depiction showing the main stent of theinvention expanded by balloon expansion.

FIG. 6 c is a schematic depiction of the deployment of the branch stentover the side branch guidewire, through one of the side openings in themain stent and into the branch vessel of the subject.

FIG. 6 d is a schematic depiction of the removal of the protectivesheath of the branch stent allowing for full expansion of the contactingportion prior to final placement and deployment.

FIG. 6 e is a schematic depiction of the compressed branch stentpositioned into the branch by the catheter with the contacting portionat least partly contacting the side opening in the main stent, but priorto full expansion of the branch stent.

FIG. 6 f is a schematic depiction of the fully expanded main stent andthe fully positioned and expanded branch stent, where the branch stentis being dilated by inflation of a balloon.

FIG. 6 g is a schematic depiction of the fully expanded bifurcatingdouble stent of the invention, positioned into the bifurcation point ina subject vessel.

FIG. 7 is a schematic depiction of the main stent with optionalexpandable portion, prior to balloon expansion of the expandableportion.

FIG. 8 is a schematic depiction of balloon expansion of the optionalexpandable portion of the main stent to cover a vessel bifurcationpoint.

FIG. 9 is a schematic depiction of the main stent with the optionalexpandable portion fully expanded to extend laterally from the sideopening of the main stent.

FIG. 10 illustrates a first stent pattern having a side hole anddifferential expansion characteristics in a “rolled out” view.

FIG. 11 illustrates a second stent pattern having a side hole anddifferential expansion characteristics in a “rolled out” view.

FIG. 12 illustrates a third stent pattern having a side hole anddifferential expansion characteristics in a “rolled out” view.

FIGS. 13A-13H illustrate the deployment of any one of the stents ofFIGS. 10-12 in a bifurcated blood vessel or a secondary stent is placedthrough the side hole of the main stent.

FIG. 14A illustrates a fourth stent pattern having a side hole anddifferential expansion characteristics in a “rolled out” view.

FIG. 14B shows a stent of FIG. 14A with first portion 804 protrudingoutwardly as a flap during stent expansion.

FIG. 15 illustrates a fifth stent pattern having a side hole anddifferential expansion characteristics in a “rolled out” view.

FIG. 16 illustrates a sixth stent pattern having a side hole anddifferential expansion characteristics in a “rolled out” view.

FIG. 17 illustrates a seventh stent pattern having a side hole anddifferential expansion characteristics in a “rolled out” view.

The rectilinear matrices shown in the drawings are intended to show theshapes of the surfaces only, and do not illustrate the actual surfacepatterns or appearances of the stent apparatuses of the invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The bifurcating double-stent apparatus 10 of the present inventioncomprises a generally cylindrical main stent 12 and a generallycylindrical branch stent 15, which are shown as fully dilated in asubject main vessel 8 and a subject branch vessel 7, as illustrated inFIG. 1.

The main stent 12 contains at least one generally circular side opening16 located between the proximal end 26 and the distal end 28 of the mainstent 12 (FIG. 2), which opening is positioned over and in registry withthe opening 48 of a branch vessel in a vessel bifurcation 50, as shownin FIG. 2. The stent 12 and the side opening are imaged during imagingprocedures either by constructing the stent of imageable materials or byplacing markers 56 at appropriate locations, such as around theperimeter of the side opening 16 in the main stent 12, and at theproximal end 26 and distal end 28 of the main stent, as illustrated inFIG. 4.

As shown in the embodiment of the invention illustrated in FIG. 4, aguidewire 20 is inserted into the vessel 8 prior to insertion of themain stent 12, and is used to guide the main stent 12 into positionwithin the vessel 8. Prior to insertion and expansion, the main stent 12is disposed around the distal end of a catheter 48 which may include aninflatable balloon 24. The main stent/catheter apparatus is thenthreaded onto the main guidewire 20 and into the vessel 8. The mainstent 12 is radially expanded by inflation of the balloon 24 until itexpands the walls of the vessel 8, and is thus affixed into place.

In a second embodiment of the invention, the branch stent apparatus 15of the present invention comprises a generally cylindrical stentcomprising a proximal end 30 and a distal end 32, as shown in FIG. 3.The proximal end 30 comprises a contacting portion illustrated here asextended loops 18, which contacting portion, when expanded, ispositioned within the lumen 58 of the main vessel 8 (FIG. 3) and atleast partially contacting the perimeter of the side opening 16 of themain stent 12. FIG. 4 illustrates the positioning of the main stent 12(without optional contacting portion) in the main vessel 8 as fullyexpanded by inflation of the balloon 24.

As shown in the embodiments illustrated in FIGS. 4, 5 and 7, the ends ofthe main stent 12 and the expandable branch stent 15 and the contactingportion 18 are visible during insertion by placing imageable markers 56around the ends of the main 12 and branch 15 stents and the contactingportion 18 and at the proximal end 30 and distal end 32 of the branchstent. Alternatively, the stent may be at least partially constructed ofmaterial which is imageable by methods including but not limited toultrasound or x-ray imaging (but not endoscopic imaging).

As shown in yet another embodiment, the stents of the invention arecombined to form a bifurcating double stent as illustrated in FIGS. 5and 6 a-g. After insertion of the main stent as described above butprior to expansion of the main stent (FIG. 6 a), the branch stent 15 isinserted through a side opening 16 of the main stent 12, a guidewire 36and a stabilizing catheter 44 are inserted through the side opening 16in the main stent 12, and into a branch vessel 7 (FIG. 6 a). Thestabilizing catheter 44 is used to place the side opening 16 in the mainstent 12 over the bifurcation point 50 in the bifurcated vessels 7 and 8(FIG. 6 a). In the embodiment depicted here, the main stent is thendeployed into position by inflation of the balloon 24 (FIG. 6 b). Duringinsertion and prior to dilation of the branch stent, the branch stent 15is disposed around the distal end of a branch catheter 54 which mayoptionally include an inflatable balloon 25, and the contacting portion18 of the branch stent 15 is held in a collapsed position by aprotective sheath 34, as shown in FIG. 6 c.

In the bifurcating double-stent apparatus 10 of the invention, once themain stent 12 is dilated and the stabilizing catheter 44 (as shown inFIG. 6 b) is removed, the branch stent 15 is inserted over the branchguidewire 36 and through the opening 16 of the main stent 12substantially as shown in FIG. 6 c, and affixed in place by withdrawalof the protective sheath 34 (FIG. 6 d) and insertion of the branch stent15 until it at least partially contacts the perimeter of the opening 16of the main stent 12 by the expansion of the contacting portions 18which are positioned at the proximal end 30 of the expandable stent, asshown in FIG. 6 e. The branch stent 15, once positioned in the branchvessel 7, may be then fully expanded by the balloon 25, as shown in FIG.6 f. The angle at which the optionally expandable branch stent 15 isaffixed depends upon the vessel structure into which the bifurcatingstent apparatus 10 is inserted. All catheters, and guidewires are thenwithdrawn from the subject vessels, leaving the main stent 12 throughwhich the branch stent 15 is inserted into the branch vessel 7, forminga bifurcated stent 10 (FIG. 6 g).

As illustrated in FIGS. 6 a-6 g, the main stent 12 is deployed prior tothe branch stent 15. This is the presently preferred order ofdeployment. It will be possible, however, in some circumstances todeliver the branch stent 15 prior to the main stent 12. In such cases,the branch stent 15 will be deployed with the contacting portions 18opened directly against the inner wall of the main blood vessel. Themain stent 12 will then be positioned over the contacting portions 18 ofthe branch stent 15 and firmly expanded thereagainst. A sheath orexpansion balloon can be used to properly align the side opening 16 ofthe main stent 12 with the opening within the contacting portion 18 ofthe branch stent 15.

In the embodiment shown in FIGS. 7-9, the main stent 40 with expandableportion 38 is positioned within the vessel 8 by the guidewires 20 (FIG.7), and affixed in place by radial expansion of the main stent 40, mostparticularly by inflation of the balloon 25 (FIG. 8). The main stent ispositioned so that the opening 16 is directly over the bifurcation point50 in the subject vessels 7 and 8 (FIGS. 7 and 8). In order to aid suchpositioning, a side branch guidewire 36 and a stabilizing catheter 44(as depicted in FIG. 7) are also inserted through the opening 16 of themain stent 40 and through the expandable portion 38 and into the branchvessel 7 (FIG. 8).

The optional expandable portion 38 of the main stent 40 is then expandedradially and in an at least partially perpendicular manner to the sidesof the main stent side opening 16 (FIG. 8). In the embodimentillustrated in FIGS. 7 and 8, a balloon 25 is deployed along the sidebranch guidewire 36 through the expandable portion 38, and inflateduntil the expandable portion is fully expanded into the branch vessel 7to cover the bifurcation point 50 of the branched vessel, as illustratedin FIG. 8. In order to extend the expandable portion 38 into the branchvessel 7, a balloon 25 disposed around a branch catheter 54 which isthreaded along the side branch guidewire 36, through the main stent 40,through the opening 16 and expandable portion 38, and into the subjectbranch vessel 7 as shown in FIG. 8. The expandable portion 38 is thenextended into the branch vessel 7 by inflation of the balloon 25, whichpushes the expandable portion 38 outward radially and lateral to theside opening, into the branch vessel 7 (FIG. 8). Once all catheters andballoons are withdrawn, the expandable portion 38 is arrayed in lateralorientation to the sides of the opening 16 in the main stent 40, andsurrounding the opening 16 into the vessel branch (FIG. 9). Theguidewires 20 and 36 are then withdrawn from the main and branchvessels.

The expandable portion 38 is illustrated as a plurality of elementswhich are attached to the peripheral edge of the side opening 16. Theelements project radially inwardly into the side opening and thus liewithin the cylindrical envelope of the tubular main stent 40 prior todeployment, as shown in FIG. 7. The elements are opened by outwardlateral deflection, typically using a balloon catheter, as illustratedin FIG. 8. The deflected elements both traverse the transition betweenthe stent and the lumen of the branch vessel and also serve as an anchorfor subsequent placement of the second stent.

In the double stent apparatus of FIG. 5 and in the main stent withexpandable portion illustrated in FIGS. 7 and 9, the main stent as wellas the expandable portions may be constructed at least partially ofand/or coated or plated with an imageable material or marked withimageable markers 56 at suitable locations, including around theperimeter of the side openings of the main stent and at the ends of theexpandable portions. In the differentially expandable stent structuresof FIGS. 10-12 (described below), a distal portion may be radiopaquewith the remainder being radiolucent. Suitable imageable materials areradiopaque, such as gold, tungsten, and the like.

When reinforcing a bifurcated vessel where both branches of the vesselrequire reinforcing, either 1) the single main stent with the expandableportion is used whereby the expandable portion extends into the vesselbranch at least partly covering the origin of the bifurcation, which maybe used alone or in combination with any conventional stent; or 2) themain stent without the expandable portion and at least one branch stentwith contacting portion are used, the branch stent placed to extendthrough at least one side opening of the main stent into at least onebranch vessel, wherein the branch stent is at least partially inregistry and contacting the edge of the side opening through which itextends. The branch stent extends laterally at varying angles to theside opening of the main stent. When treating a bifurcated vessel wherethe area to he treated spans the bifurcation and unobstructed access tothe unstented vessel is required, the main stent may be used either withor without the expandable portion, wherein at least one side opening isplaced over the bifurcation point.

The stent apparatus of the invention may be constructed from anynon-immunoreactive material, including but not limited to any of thematerials disclosed in the prior art stents which are incorporatedherein by reference. It is intended that the stent apparatuses of theinvention may further be at least partially constructed of, or marked atcertain points with, a material which may be imaged, most particularlybut not limited to by x-ray and ultrasound.

The stents of the invention may be deployed according to known methodsutilizing guidewires and catheters, which are then withdrawn from thesubject following deployment of the stents. The subject stents may beself-expanding to conform to the shape of the vessel in which they aredeployed, or they may be expanded utilizing balloon catheters, or by anyother method currently known or developed in the future which iseffective for expanding the stents of the invention. It is contemplatedthat prior to deployment the stents will be in a collapsed state, andwill require either mechanical expansion (such as, for example, byballoon expansion) upon deployment or, for self-expanding stents, willrequire that the stent be confined to the catheter until deployment by,for instance, a retractable sheath, in which the sheath is removedduring deployment and the stent self-dilated. The stents of theinvention and the optional expandable portion of the main stent of theinvention expand radially from their longitudinal axis, lateral to theside opening of the main stent. Other methods of dilation of the stentsof the invention may exist, or may become available in the future, andsuch methods are contemplated as being within the scope of thisinvention. The stent 100 shown in FIG. 10 can also be described ashaving a first portion 110 comprising a plurality of serpentine rings112 and a second portion 120 comprising a plurality of serpentine rings122. Each serpentine ring 112, 122 has a plurality of elements thatinclude struts 134 interconnected by turns. The plurality of serpentinerings 112 of the first portion 110 includes a plurality of firstserpentine rings 112 a and a second serpentine ring 112 b. The secondserpentine ring 112 b has a first end which is engaged to the continuousband 104 at junction point 500 a. The second serpentine ring 112 b has asecond end which is engaged to the continuous band 104 at junction point500 b. As shown in FIG. 10, the second portion 120 comprises a pluralityof serpentine rings 122 which include a plurality of first serpentinerings 122 a and a second serpentine ring 122 b. The second serpentinering 122 b has a first end which is engaged to the continuous band 104at junction point 500 c. The second serpentine band 122 b has a secondend which is engaged to the continuous band 104 at junction point 500 d.

Referring now to FIGS. 10-12, the present invention further providesstent structures having differential radial expansion characteristics.In particular, tubular stent structures having side holes, generally asdescribed above, are configured so that a portion of the stent on oneside of the side hole will expand at a different yield or thresholdforce than a portion of the stent on the other side of the side hole.Such different yield forces or pressures may be achieved in a variety ofways. For example, referring to FIG. 10, a stent 100 is illustrated in a“rolled out” view, i.e., the tubular stent is broken along an axial lineand then rolled out in the resulting pattern shown in the Figure. Thepattern shown in FIG. 10 is prior to expansion. The stent 100 includes aside hole 102 defined by a continuous band 104 having a plurality ofloops 106 projecting into the open interior of the side hole. The loops106 are an integral part of the band 104 and will, prior to expansion oropening, lie within the cylindrical envelope of the tubular body of thestent. The first portion 110 of the stent lies on one side of the sidehole 102 and is defined by a plurality of serpentine rings 112. Theserpentine rings are joined by axial expansion spring structures 114 sothat the stent may be bent as it is introduced and/or deployed. A secondportion 120 of the stent 100 is formed on the other side of side hole102. The second portion is also defined by the plurality of serpentinerings 122 which are generally similar in structure to the rings 112 ofthe first portion 110. Each of the portions 110 and 120, however,include an axial spine 130 and 132. The axial spine 130 of the firstportion 110 comprises simple W-shaped structures including outermoststruts 134 which open at a relatively low expansion force on theadjoining hinge regions. In contrast, the axial spine 132 of the secondportion 120 comprises box elements 138 which require a greater expansionforce to open. Thus, in deployment, the first portion 110 will yieldfirst to allow partial opening before the second portion 120 begins toopen. The stent 200 shown in FIG. 11 can also be described as having afirst portion 204 comprising a plurality of serpentine rings 208 and asecond portion 206 comprising a plurality of serpentine rings 210. Eachserpentine ring 208, 210 has a plurality of elements that include strutsinterconnected by turns. The plurality of serpentine rings 208 of thefirst portion 204 includes a plurality of first serpentine rings 208 aand a second serpentine ring 208 b. The second serpentine ring 208 b hasa first end which is engaged to the continuous band 104 at junctionpoint 500 a. The second serpentine ring 208 b has a second end which isengaged to the continuous band 104 at junction point 500 b. As shown inFIG. 11, the second portion 206 comprises a plurality of serpentinerings 210 which include a plurality of first serpentine rings 210 a anda second serpentine ring 210 b. The second serpentine ring 210 b has afirst end which is engaged to the continuous band 104 at junction point500 a. The second serpentine band 122 b has a second end which isengaged to the continuous band 104 at junction point 500 b.

A second stent structure 200 having differential expansioncharacteristics is illustrated in FIG. 11. A side hole 202 is formedfrom a continuous band of material, generally as described for FIG. 10.A first portion 204 and second portion 206 of the stent each comprise aplurality of serpentine ring structures 208 and 210, respectively. Whilethe specific geometries differ, the structures of stents 100 and 200 aregenerally the same, except for axial spine portions 220 and 230 in thefirst portion 204 and second portion 206, respectively. The first spineportion 220 comprises a simple U-shaped loop having a pair of strutsjoined by a simple C-shaped hinge region. The spine 220 will thus openat relatively low expansion forces. In contrast, the axial spine 230 ofthe second portion 206 comprises a serpentine element which allows foraxial expansion but does not permit radial expansion at all. Thus, thefirst portion 204 will begin opening at much lower expansion forces orpressures than will the second portion 206.

A third concept for providing differential expansion is illustrated inFIG. 12. Stent 300 comprises a side hole 302 (which is shown in halvesin the illustration), a first portion 304, and a second portion 306. Thefirst portion 304 and second portion 306 each comprise serpentine rings308 and 310, respectively. Differential expansion, however, is notachieved by providing a particular axial spine region, but rather byhaving different characteristics in the serpentine rings 308 and 310.The serpentine rings 308 have axially aligned struts joined by simplehinge regions. The length of the struts is relatively long (compared tothose in the second portion 306 as described below) so that the ringswill open at a lower expansion pressure or force. The serpentine rings310 of the second portion 306 have relatively short axial struts definedby hinge regions each having two bands. Such structures require agreater expansion force than do the serpentine rings 308 of the firstportion.

A fourth concept for providing a differential expansion stent isillustrated in FIGS. 14A and 14B. Stent 800 comprises a side hole 802which is defined by parallel struts 804 and curved struts 806. Struts804 can be expanded radially outwardly, forming a flap during stentexpansion as illustrated schematically in FIG. 14B. Accordingly, struts804 can be positioned to support the proximal section of a bifurcatedvessel during stent expansion. As described above, portion 805 of stent800 will preferentially expand at a different rate than portion 807 ofstent 800.

A fifth differential expansion stent 900 is illustrated in FIG. 15. Thestents shown in FIGS. 15-17 are examples of stents with side holes thatare defined by a side branch member that has discontinuities. Stent 900has a side hole 902 which is tear drop shaped, offering the advantage ofeasier expansion of the strut members 904 during differential expansionof the stent 900. The side branch member has two strut members 904 whichare connected to one another by connectors 906. The strut members 904are mirror images of one another. In this embodiment, the connectors 906of the discontinuous side branch member have different configurationsthan the connectors 906 engaging adjacent circumferential rings ofstruts. As shown in FIG. 15 the discontinuous side branch member has twoconnectors 906 that have different configurations with one connector 906being U shaped and one connector 906 being zig-zag. Due to the tear dropshape of the side hole 902 in this embodiment, the circumferentiallength of the side hole 902 varies from the proximal region of the sidehole 902 to the distal region of the side hole 902.

A sixth differential expansion stent 920 that has a side opening 922 isshown in FIG. 16. Wavy bridges 924 connected to horizontal strut members926 are adapted to provide superior flexibility in axial bending. Wavybridges 928 around the perimeter of side opening 922 operate to provideaxial flexibility about the side hole 922. Note that wavy bridges 924,928 have substantially the same configuration. In this embodiment thediscontinuous side branch member comprises at least two struts 926 andat least two connectors 906. As shown in FIG. 16, the side branch memberhas a first strut 926 a, a second strut 926 b, a third strut 926 c, afourth strut 926 d, a fifth strut 926 e, and a sixth strut 926 f. Theside branch member also has a first connector 906 a, a second connector906 b, a third connector 906 c, a fourth connector 906 d, a fifthconnector 906 e, and a sixth connector 906 f. As shown in FIG. 16, theconnectors 906 of the side branch member can have substantially the sameconfigurations or different configurations. For example, some of theconnectors 906 a-c, e-f are zig-zag, with some connectors havesubstantially the same zig-zag configuration, e.g. wavy bridges 928 andone connector 906 a has a zig-zag configuration that is different fromthe other zig-zag configuration. Also, one connector 906 d has aU-shaped configuration.

A seventh differential expansion stent 940 is shown in FIG. 17. Stent940 has a side hole 942 which is oval in shape. In this embodiment, thediscontinuous side branch member comprises four struts and fourconnectors 906 a,b. Two of the struts being long struts 944 and two ofthe struts being long struts 946, with the pair of long struts 944 atone end of the side opening 942 and the other pair of long struts 946 atthe opposite side of the side opening 942. The long struts 944 and 946are curved and have a taper so that one end of the strut is wider thanthe other end of the strut. In this embodiment, the side branch memberhas two connectors 906 that have a zig-zag configuration and twoconnectors 906 that have a U-shaped configuration. The connectors 906that have a zig-zag configuration are wavy bridges 948 which facilitateaxial bending. In this embodiment, the two connectors 906 that have azig-zag configuration are positioned opposite one another and the twoconnectors 906 that have a U-shaped configuration are positionedopposite one another at the ends of the side hole 942.

It will be appreciated that numerous other specific designs may beprovided for differential expansion. What is important to the presentinvention, however, is that at least a portion of the stent on one sideof the side hole, usually the entire length of the stent on that side ofthe hole, will be able to open prior to opening of the stent on theother side of the side hole. Preferably, the first portion of the stentwill open at a balloon expansion pressure in the range from 1atmospheres to 10 atmospheres, while the second portion of the stentwill open in response to a balloon expansion pressure in the range from2 atmospheres to 18 atmospheres.

Referring now to FIGS. 13A-13H, deployment of stent 100 will bedescribed. While reference is made to stent 100, it will appreciatedthat the same method could be used as well with either of stents 200 or300. Initially, a pair of guidewires GW1 and GW2 will be deployed in thelumen, typically a bifurcated blood vessel, so that guidewire GW1extends through the main lumen of the main vessel past the ostium O ofthe branch vessel BRV. The second guidewire GW2 will be advanced throughthe lumen of the main vessel and into the lumen of the branch vesselBRV, as illustrated in FIG. 13A. The stent 100 will then be introducedover the guidewires on a delivery catheter 400 having an expansionballoon 402, where the stent is crimped over the expansion balloon. Asheath 404 is disposed in the second portion 120 of the stent with itsdistal tip (not shown) terminating immediately before the side opening102. The assembly of the stent 100, delivery catheter 400, and sheath404 will be delivered with the first guidewire GW1 passing through aguidewire lumen of catheter 400 and the second guidewire GW2 passingthrough the sheath 404, as illustrated in FIG. 13B. Initial alignment ofthe side hole 102 of stent 100 is achieved by advancing the stent sothat the side hole lies close to the ostium O.

After an initial rough alignment is achieved, the balloon 402 isinflated to an initial inflation pressure which opens the first portion110 but which leaves the second portion 120 in its substantiallyunexpanded configuration, as shown in FIG. 13C. Such partial openingallows the sheath 404 to be advanced over guidewire GW2 to better alignthe side hole with the branch vessel BRV, as shown in FIG. 13D. Thesheath provides much greater stiffness than the guidewire, permittingmanipulation of the partially deployed stent 100 to achieve the betteralignment.

Referring now to FIG. 13E, after alignment is achieved, the balloon 402will be inflated to a greater inflation pressure to open the secondportion 120 of the stent 100 as well. A balloon catheter can then beadvanced over the second guidewire GW2 so that balloon 502 can beexpanded within the side opening 102 to open the loops 106, asillustrated in FIG. 13F. In many cases, this will be sufficientdeployment for the stent where the loops provide the necessary anchoringand transition at the ostium O.

Optionally, a secondary stent 600 may be introduced as illustrated inFIGS. 13G and 13H. The stent 600 is introduced over a balloon 702 onballoon catheter 700. The final deployment configuration is illustratedin FIG. 13H.

It is intended that the invention include all modifications andalterations from the disclosed embodiments that fall within the scope ofthe claims of the invention.

1. A stent, the stent comprising a plurality of first serpentine rings,each first serpentine ring comprising a plurality of first struts and aplurality of second struts, each first strut having a first length, eachsecond strut having a second length, the second length being greaterthan the first length; each first serpentine ring further comprising aplurality of first turns and a plurality of second turns; each firstturn engaging two first struts and each second turn engaging two secondstruts.
 2. The stent of claim 1, the stent having a first end, eachfirst turn oriented towards the first end of the stent, and each secondturn oriented towards the first end of the stent.
 3. The stent of claim2, wherein the first turns are aligned with one another, the secondturns are aligned with one another, and the first turns are offset fromthe second turns.
 4. The stent of claim 1, each first serpentine ringfurther comprising a plurality of third turns, each third turn engaginga first strut and a second strut.
 5. The stent of claim 4, each firstturn and each second turn oriented in a first direction and each thirdturn oriented in a second direction, the first and second directionsbeing opposite directions.
 6. The stent of claim 4, wherein the thirdturns are aligned with one another.
 7. The stent of claim 1, each firstturn having a first circumferential extent and each second turn having asecond circumferential extent, the first circumferential extent beinggreater than the second circumferential extent.
 8. The stent of claim 1,wherein a first distance separates two first struts engaged by a firstturn and a second distance separates two second struts engaged by asecond turn, the first distance being greater than the second distance.9. The stent of claim 1, adjacent first serpentine rings being engagedby a plurality of first connectors, each first connector extendingbetween a first turn of one of the adjacent first serpentine rings and afirst turn of the other of the adjacent first serpentine rings.
 10. Thestent of claim 9, wherein adjacent first serpentine rings engaged by aplurality of first connectors define a plurality of first openingshaving a first shape.
 11. The stent of claim 10, wherein adjacent firstserpentine rings engaged by a plurality of first connectors furtherdefine a second opening having a second shape, the first shape beingdifferent than the second shape.
 12. The stent of claim 11, the stentfurther comprising a side hole defined by a continuous band having aplurality of loops.
 13. The stent of claim 12, the side hole having athird shape, the third shape being different than the first shape, andthe third shape being different than the second shape.
 14. The stent ofclaim 1, the stent having a first end, the stent further comprising aplurality of second serpentine rings, each second serpentine ringcomprising a plurality of first struts and a plurality of second struts,each first strut having a first length, each second strut having asecond length, the second length being greater than the first length;each second serpentine ring further comprising a plurality of firstturns and a plurality of second turns; each first turn engaging twofirst struts and each second turn engaging two second struts; each firstturn of the first serpentine rings oriented towards the first end of thestent, and each second turn of the first serpentine rings orientedtowards the first end of the stent; each first turn of the secondserpentine rings oriented towards the second end of the stent, and eachsecond turn of the second serpentine rings oriented towards the secondend of the stent.
 15. The stent of claim 14, the plurality of firstserpentine rings forming a first portion of the stent and the pluralityof second serpentine rings forming a second portion of the stent.